Least-Squares Local Tuning Frequency Estimation for Choir Music

Presented at the 131st AES Convention, 2011 October 20-23, New York, USA

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Choir conductors often have to deal with the problem that the tuning pitch of a choir tends to decrease gradually over time. For that reason, we present an algorithm which measures and displays the tuning frequency evolution for polyphonic choir music over time. Basically, it analyzes the short-time Fourier spectrogram, picks out the most important peaks, and determines their frequencies. From these frequencies, the algorithm determines the concert A pitch that leads to the smallest least-squares-error when the measured frequencies are sorted into a semitone grid. The algorithm has been implemented on the Android platform and works in real-time.


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PDF (2 MB)

Sound Examples for Figure 5

Gospel choir singing "An Irish Blessing". All sound examples are stored in the FLAC format (Free Lossless Audio Coding). Details and decoding software can be found here.